Telephone system



Aug- 17, 1943. A. s." lvxmrnxsgA TELEPHONE SYSTEM Filed July 2, 1942 9sheets-sheet i Aug. 17, 1943.` A. s. MAR-rms 2,327,201

` TELEPHONE SYSTEM Filed July A22, 1942 Sheets-Sheet 2 /NVENTOR A -By-A. 5. MART/NS ii if." 'l' Arron/VEP Aug. 17, 1943. A.s. MARTlNs2,327,201

TELEPHONE SYSTEM Filed July 22, 1942 9 Sheets-Sheet 5 HRGINL /NVENroR ByAS. MART/NS g ATTORNEY U8 17, 1943- ,A. s. MARTlNs 2,327,201

' I TELEPHONE SYSTEM Filed Ju 1y 22, 1942 s sheets-sheet 4 /NvENroR A.S. MA R T/NS ATTORNEY 9 Sheets-Sheet 5 m. .QQ

A. s. MAR'lNs TELEPHONE SYSTEM Filed Jul'y 22, 1942 /Nl/Nrof? A. 5. MA RT/NS er K y AT rom/EV Aug. 17, 1943.

Aug. 17, 1943. A. s. MARTINS 2,327,201

TELEPHONE SYSTEM Filed July 22, 1942 9 Sheets-Sheet 6 Ii n ATTORNEY Aug.17, 1943.

A. s. MARTINS TELEPHONE SYSTEM Filed July .22, 1942 9 Sheets-Sheet 7 N.um

ATTORNEV Aug. 17, 1943. A. s. MARTlNs 2,327,201

TELEPHONE SYSTEM Filed July 22, 1942 9 sheets-sheet a /N f E RME DIA TEGROUP j ma /NVENroR A. S. MART/N5 i A7' TORNEV Aug. 17, 1943. A. s.MARTlNs TELEPHONE SYSTEM Filed July 22, 1942 9 Sheets-Sheet 9' /NVN To@A. 5. MA R T/NS A7' TORNE Y E Patented Aug. 1.7, 1943 alfine ze f'chen-ne notify the operator that a diiierent condition has beenencountered. rIhis might be terined a syncopated flash since the timingrelation of the dark and light periods has been changed. X/Vhereas, thenormal flashing recall signal consists o roughly equal periods of lightand dark, the new or syncopated signal consists of a prolonged period oflight and a shortened period oi dark.

In the present system the attendants connector for local calling iscontrolled over a threewire circuit having the usual tip, ring andsleeve conductors. Inthe case where subscribers at a distance are to bereached a two-wire circuit is employed. The cord circuit makesconnection to a three-wire connector circuit but this leans over atwo-wire circuit to the distant connector. In this case the recall ismade in the usual way by a momentary opening oi the ridge across ti etip and ring conductors at the subscribers end of the line and this, inturn, starts the flashing recall circuit ci the cord to function. If abusy condition is encountered, however', the signal is passed over thetwo-conductor circuit from the distant connector to the local connectorcircuit by grounding of one of the two-conductors whereat the localconnector circuit translates this into a circuit condition whereinthesecond synchronized interrupter in the connector circuit issuperimposed on the regular interrupterrof the cord circuit to form thissyncopated flash. In accordance with another feature ci the invention,therefore, o. diierential relay in the connector circuit is employed torespond to a single wire ground transmitted from the connector.

Reference is made to the copending Yapplications Serial No. 451,863,iiled in the name of C. D. Koechling, and Serial No. L151,362 filed inthe name of H. H. Abbott von evenV date herewith, both of whichapplications cover inventions based mainly on the same disclosure asthat herein set forth.

Other features will appear hereinafter'.

The drawings consist of nine sheets of circuit diagram. l

Fig. 1 is a schematic circuit diagram showing the general plan ofoperation and indicating the arrangement of the remaining iigures;

Figs. 2 and 3 placed with Fig. 3 to-,the right of Fig. 2 show a cordcircuit and Fig. 4 placedY below Fig. 3 shows the operators telephoneand dial circuit all used at the manual switchboard used in connectionwith a dial private branch exchange; I

Fig. 5 shows an outgoing trunk circuit cooperl ating with the cordcircuit of Figs. 2 and 3 by means of which the operator may control thedistant connectors of Figs. 6 and 7;

Fig. 6 shows a distant connector overvwhich an operator may reachanyoneV of a group of individual lines;

Fig. 7 shows a similar circuit arranged for trunk hunting over which anoperator may reach a group of lines arranged in subgroups;

Fig. 8 shows an operators connector cooperating with the cord circuit ofFigs. 2 and 3 over which an operator may reach any one of a group orindividual lines; and i Fig. 9 shows a similar vcircuit arranged fortrunk hunting over which an operator may reach a group of lines arrangedin subgroups. v

The system herein disclosed is a dial private branch exchange system 'soyond the capacity of the manual attendants board. It is common practiceto .supplement a large that it is'bc-v dial private branch exchangesystem with a manualattendants board where incoming calls are answeredand certain other special service is given. Generally speaking, a manualboard has a capacity of about ten. thousand lines or can handle onlyfour digit numbers. But it is possible to employ a system of muchgreater capacity for private branch exchange service. The present systemis shown as a five-digit system, though it may be of even greatercapacity.

Since the number of lines to be served is beyond the capacity of amanually operated switchboard the operator is not given direct access toany of the lines but selects an outlet bearing the rst three digits ofthe number of the wanted line and then dials the last two digitsthereof. Thus, by way of example, if the operator wishes to establish aconnection to line numbered 12345 she will insert her calling plug intoa jack designated 123 and then dial 45. By thus setting up -a connectionpartly by a manual operation and partly by an automatic or dialingoperation the operator at such a switchboard may reach any one of anumber of subscribers more numerous than could be reached byconventional methods.

VIn Fig. 1 there are shown two ordinary private branch-exchange linesterminating in stations I and 2, each equipped with a dial. Thesestation lines appear in a line nder 3 and by dial control may operate afirst selector 4, a second selector 5, a third selectorv G and aconnector 'I Yall in conventional manner. Thus these stations may beinterconnected by ordinary and well-known means. As indicated in thisschematic anyone of such ordinary stations may dial 0 and reach anoperator through an answering jack appearance 8. Such a station bydialing the digit 9 may reach a central oice 9 over an outgoing trunkID. In the same manner any one of these stations by dialing .8 may reacha distant private branch exchange I I over va tie line I2.

There may be provided certain special lines for'high ranking officialssuch as those terminating in stations I3 and I4 which do not appear inline finders, but on the other hand, have special switchboardappearances YI5 and I6, respectively, so that outgoing service is on amanual basis. These lines have appearances in the bank of the connectorsso that they may be reached automatically.

Incoming central office lines and tie lines have manual appearances suchas I'I and I8.

The operator may answer a call at any one y or"V the appearances 8, I5,I6, Il or I8 by means v`lish connections to any one of the stations ofthe private branch exchange. It is understood, of course, that theoperator may also extend connections to the central ofice 9 and thedistant private branch exchange II, but these arrangements are wellknown and do not form any essential part of the present invention. Itmay also be noted that the distant private branch exchange I I may bethe same as the distant pri- .vate branch exchange indicated in thebroken line rectangle in the lower right cornerof this iigure. In theone case the tie line vI2 leading to the private branch exchange isanswered by the operator thereat and in the other case a connectionmaybe extended from jack 22 or 23 'directly to a subscriber in suchdistant private branch exchange. f

eonnetion' to ally." ofn olie" scribe atedrby' trie shown in Figs. 2 and'redk "eircuit 3 is. arranged to dooperate With variouslnes"provi"ded"with a connection to battery on Ithe =sleeves thereof.When of 'the rear cord 3| is inserted in the jack `associvthe plug ated"witha `lighted line-lamp; such" as that* assoeiatedwith `jack l5 forinstance; a vCircuit Will be `Vestablished frem'battery on the sleeve ofthe asso'eiated" line circuit-through "the, sleeve Si Land thenceiin'series through the' windings oflA and' through a small positivelbatteryrelays '33 of plug "to ground. -Both relays "33T and* 34 operate in thiscircuit-though the relay'iperformsno use- -fuVULnetion at this time.

`ture and 'front contactand "the winding 35"'t0" battery''tzvl'lereupon`vRelay 34 'operated elo'sesia 'circuit fromground through Yitsarma-` lofrelay relay'- operates and at its' afl'rnature'` andY hackA Contactopens a circuit for relay 36. Through the" operation' of relay aAcircuit is closed 'from the tip of the 'plug Vv:SL-springs, 24 andV 3ofthe ringing' key 3l, upper the 'key `arrrlature land front'contact'ofz relay`35,

armature 3 and back Contact ofrelay'll, upper vWinding of relay' lll toground; yAtV thesame time "a Circuit may be 'traced' `frolrrtlle-ring'of plugY 3l througdsprings 5 and d1 of the* ringing key' 3l,

lower A Winding the lower Winding of relay 4lto1bfattery. 38j and'lfboth dp'erate'due V'through the circuit just described "andorrelayS8,-fs'prings 'H and llfljof 'key 3S, armaturer 6 and backcontact'of relay 4i), Relays to current llovvng over the elear'lnderstanding ofthenature'of-'suchcal1-` he circuit referencel 'may be "had" to. the ap-"ing li plcatlon led by 'Bascoln "and Lambertyyerial Relay' 88 operatedi-prer'fents*the rear 'cord su-` pervisory larnpI 32 from lightingWhilethe relay @1 l opeiatea 15e; Ntime.

formation from for the front Y "operating relays 43 and Min series.

rfo'rms luse flvll'ffunction fat this.` '55 Relay 43)operatedestablishesa cirelitf'from l{grourll "its armature and front'Contact through leperatiol'r of relay 45. f 'Relay'i in" operatingeslPtablisl'les; a circuit from ground,its"arnrature and relay 4G tobattery whereupon Vrelay 46 becomes,V operated.

'circuit rnay'n'ow'be/tracedA from ground, rei 70 V.istarl'ee armatureand 'front- `contantp-f relay 38,arlnature I Varldnbaek eontactiof relay43,the lower Winding of relay 4l, springs fj a-nl pf key 349;frontontaet and armaturel5J of` relay 45 to battery. Relay 4l operatesand locks in a circuitr V45: and rient Contact 'sol 60 thev ring-ing'current v'ilows winding of relay 38, springs 4 and 5 of ly'Fto the/ringor plugj ,3 i .v ThisY circuit,V though' closed z byxarrnature'- 2-ofrelay 45; isJ openedby armature il of relay"i Relayf` operated removes35 thehusyftestleadtrom-the"t'ip---of-jthe front VAcord;'(oenneets thetip "-andj ringfof -the 1- cord through the contacts ofrelay51-and-disconnects `zyattery through-resistancegl thelring'of thefront cord plug. AARelayY 45 operatedconnects 4o the Windingsjofrelay-tothefrolltcontactsof s-anfl-frontcontaet of .contact 2 andarmature l' to rand armature l of relay 45.

(D) No bridge is connected across lease causing relay 49 to operateunder -of relays 55 vand 33.

33, armature 3 of armature 2 oi ground. The lighting of from battery,relay 45, springs Y and back contact of relay 50, winding of relaylthroughl resistance 55 K through itsV front contact and armature'Z tothe the callingstation as an indication that ringing current' is beingconnected to the called station line'.

When the receiver called station is removed from vthe switchhook thetripping relay 51 operates. The relay 51 thereupon substitutes thewinding ol relay 52 to the tipand ring of the called line in place ofthe source of ringing current 59 and locks through'its lower winding,its

the front contact Relay 52, now in circuit with the called station,operates and causesthe front cord supervisory lamp to be extinguishedand the relay 54 to operate through its lower winding. The circuit forrelay 54 may be traced iromgroundresistance 55, armature and frontcontact otrelay 52, armature 3 and back contact of relay 53, lowerwinding of relay 54, front contact and armature 1 of relay 46 to springs3 and 9 of key 33, front Contact and armature 5 of relay 45 to battery.Relay 54 locks in a circuit from ground, normal contacts of armature Ilof relay 5B, armature 2 and iront contact of relay 54, upper winding ofrelay 54 through back contact and armature 3 of relay 55 to battery overthe circuit hereinbefore described. Relay 54 therefore ylocks undercontrol of relays 50, 45 and 46 and partly provides an operating pathfor relay 53.

From the foregoing wel can summarize as follows;

(A) Battery and ground for the calling station are furnished by the cordcircuit through the -wiridings of relaysi4l and 33.

(B) Battery and ground for are furnished by the f cord circuit throughwindings of relay 52.

(C) The front and rear cords are coupled through condensers 63 and 64.

the tip and ring of thecord, except the ringing relay 61 which has nouseful purpose at this time.

' When the receiver is replaced on the switchhook at the callingstation, relays 4| and 38 re rIhe circuit for relay 49 battery, armature6 and 45, springs 9 and 8 of key may be traced from front contact ofrelay windingof relay Vl5 through the normal contactsv relay 49,armature 4 and front contact of relay 41, back contact and armature ofrelay through resistance 43 to ground.

Relay 49 operated locks'through its frontI contactu and armature 2,iront Contact and armature 5 of relay 35, springs 1 and 6 of key 39 toground. The rear cord supervisory lamp 32 is now energized in a circuitfrom battery, lamp 32, armature 2 and front contact of relay 35,armature 4* and front contact of relay 49, resistance 48 to: lamp 32.operates as a disconnect signal.

When the receiver at the called station is replaced on the switchhookrelay 52 releases cansing relay 53 to operate under control of relays.55, 4E and 45. A circuitV lfor relay 53, may be traced armature 6 andirontr contact of 9. and 8 of key 39, armature 3 53 through thenormalcontacts oi-armature 2 of relay 53, iront Contact and armature lof relay 54, back contact and armature of relay 52 to ground. Relay 53locks the called station,

and back contact of relay 5),V

control" normal contacts or armature 4 ci relay 53 to ground.Theoperation ofrelay 53`n'ow lights the front'cord supervisory lamp in acircuit which may be traced from battery, lamp 5l, front contact andarmature 3 of relay-46, armature S and front contact of relay 45, frontcontact and armature l of relay 53, resistance 55 to battery.

l This lighting olarnp 5l operates as a disconnect Ii before the plugsof the front and rear cords are withdrawn from the jacks `the switchhookat the calling station is operated and released to recall the attendant,the relays 4i and 38 will release and reoperate. The relay in releasingcauses the operation of relay in the manner hereinbefore described. Uponthe reoperatlon of relay 38 the rear cord supervisory lamp is nowconnected in a circuit which may be traced from battery, lamp 32,armature 2 and iront Contact of relay 35, armature 4 and rcnt contact ofrelay 45, through the resistance 48 and in parallel therewith, thearmature and front Contact of relay 38, armature I and front contact ofrelay 49 to the ashing recall lead 55 which essentially suppliesinterrupted battery to periodically shunt the lamp 32. This causes thelamp to ilash. The attendant then operates the talking and dialing key62 causing relay 53 to operate which releases relay 45. Relay '45released, stops the flashing of the lamp 32.

if the switchhook at the'called station is operated and released, relay52 releases and reopcrates. Upon the release of relay 52 relay 53 isoperated, as hereinbefore described. With relay 52 reope'rated the frontcord supervisory larnp 5l is connected in parallel with the flashingrecall circuit 55 n'a mannersimilar to that hereinbefore described sothat lamp 5i now flashes. The attendant then operates -the talk and dialkey @2, causing relay 53 to operate., Relay 50 operated'releases relays53 and 54. Relay 53 released stops the flashing of the lamp. When thetalk and dial key 32 is restored to normal,=r elay 5G releases and relay54 reoperates, as described hereinbefore.

The above description applies to the use of the cord circuit when aconnection is being made between two local lines as, for instance, aconnection between the stations i3 and ill.l In the schematic shown inFig. l it is not contemplated that the calling cord 2l will be used forA Vdirectly calling a local substation though it is capable of this-usein the manner .above described.` Y f y It should bejnoted that both theansweringand calling cords have two relays in their sleeve circuits, oneotwhich is marginal. Thus, for instance, the sleeve of the answeringcord has the two relays 3 3 and 34 in series,the relay 34 being marginaland only operating when a line sleeve o lower resistance is encountered.In the same manner the sleeve of the calling plug 42 has the relays 43and 44 in series with it, the relay 44 being marginal.

It will be noted in the description to follow that thesleeve of the lineleading toan attendants connector as, for instance, from the Yjackappearances 22 to 25, inclusive, has a high resistan-ce when it isselected and maintains this high resistance until certain operations arecomplete'd, after which the resistance is lowered. Therefore on a callfrom va station to another station via an attendants connector-themarginal relay of the calling cord will not be operated at first.

Y When completing a call froman attendants trunks, such as thatterminating in Vthe jack 8, or from a manual station, such as thosel'fei'nfli-V nating in the jacks l5 and I6, to a station via anattendants connector, the operation when the call is answered with therear cord is the same as described hereinbeore. However, when thefrontcord is inserted in the lack associated with an attendantsVconnector relays 43, 4'5 and @D operate since the sleeve resistance 'ishigh. Relay M operateddisconnects the relayrbattery supply trom therearcord but the calling station receives battery from the connector in theinanner which will be described hereinafter. When the foperators dialyis 'moved olf 'normal for the' first digit the rear cord is fed batteryand ,ground from the telephone and dial circuit and the front and rearcords are separated in the dial circuit. The attendant then dials thetwo digits required to bring the connector to the desired line.

'The attendants connector will 'out through on the called' line iff itis 4idle and the battery and ground from the tip and ring or theconnector will be removed. At this time the connector also changes theresistanc'elon the ia'ok sleefve from high Sto low. 'The change to a"low sleeve resistance causes relays 44 and 4S to operate which 'in tum-fcause's relay 4u to release; 'Ine release or relay dlreconnecfts relayM to the rear cord and separates the 'rear and iront cords by condenserses and fsa. The connector is nele olf n'orrnal under control ofthesleeve after 'out through and the tip and ring ot the lront cord areconnected to the back contacts yof the trilpping relay 51 to transmitmachineeringing cur rent 'to the called subscriber.. Y Audible ringingtone is transmitted toward the rear cord through condenser 68 asherelnlcefore descrl'bed.- Relay 1S closes the windings 'of relay 52 tothe-front contacts -of 'the trim-ing relay 51 to supply talki-ng batteryto the called line after tripping relay 51 operates upon the response ofvthe :called When the 'called stati'on'answersg relay 57 operasesandrelays 52, '5S and 54 `function as fdescribed hereinbefore. Thetalkin-g, signaling; supervisionq disconnect Vand flashing recall willbe the as described hereinloefore. Y

I the attendants connector yis dialed-.to a busy line the sleeve becomeslow in resistance and the battery and ground on ythe tip and ring of theconnector are removed and replaced by a bridge intermittently applied.The ringing from the cord is tripped 'through ythis bridge. Il the zat'-tendant has restored the talk and dial :key 62 the intermittent bridge'across the tip :and ring" will operate and 'release relay fst'artingthe flashing recall signal 5i on the front cord lamp. If theattend'ant:has not :restored the talk and dial key E2 she will `receive -anaudible busy indication.

It is particularly to be noted that the interrunter in the attendantfsconnector circuit which intermittently applies the bridge to ti'letipand ring ci the calling cord 62 is of 'onfeelialf the rate of' theinterruptor 6 6. By way of example,

the'interr-upter 66 applies batteryv to the lead 65 V at the rate of1,20v impulses per minutewhile the 'interrupter in the attendantsconnector circuit runs at the rate of v6() interruptions per minute.

- Since the interruptor in the attendants connector circuit operates therelay 52 it will there'- fore render the dashing recall circuit of thiscord circuit electve on yevery other interruption thereof so'thattheeffec-t is that the lam-p 5i will be vlit approximately three-tenths ofa .period and dark the other .Seifen-tenths thereof. The -signal for therecall is a steady ilash-ing at the rate of 12S interruptions perminute, while the signal for the encounter of a busy condition is thistso-called syncopated signal wherein every other nash of the signal inits ordinary working is rendered eiective, Since the interrupter of theattendants conneclxnr circuit and the interruptor 6 .are both operatedtrolhmthe -same power plant they may Aboth be on the same shaft and therelation between them maybe fixe The ope-ration of the oord circuit cn aconnection between a central olce call and a station is as follows: theincoming central ollce call is answered with the rear cord 3l Yin theusual manner and theoperation is. different from thatdescribedhereinbefore in that a high sleeve resistn ance .is lencountered whichdocs not allow the marginal relay 34 to respond. Since the inarginalrelay does not respond, therefore relay 35 does not operate.

As a result a connection is established from ground-y springs Ei and 7of key 39, amature 5 andl back contact ci relay 35, front Contact andarmature lof relay 33 winding of `relay 36 Ato battery. is a result ofthe operation yof relay 36 a connection may be traced from -ground atthe armature and back contact Aof relay $4, armature 4 andlfront contactof relay 6, winding of relay 48 te battery andground whereupon relay 4Gbecomes operated. The operation of these relays connects a bridge acrossthe cord which may be traced from fthe `tip of plu-g 3l springs and 3 ofthe ring-ing key 37, fron-t contact 'and armature 3 yof relay 355,retardation coil 8-, armature 4 and back contact of relay 4l, armature 8and iront contact ofrrelay 35@ springs 4 5 of ringing key 3J to the ring-of plug `3l 'I'hisjbridge serves as a signal' on the central officeline lthat the call has been answered and will .serve to trip ringingand .perform the other usual lfunctions required 4in a caseof this kind.

Whenthe Sir-.ont 'cord is-inserted in the jack of anattendantsfconnector relay 33 ,operates and causes the operati'ongofrelay 47 Aon its' lower winding. .Y l

A circuit may be traced from ground -on the tip of cord 3l, springs 2and '3 'of ringing key 31", upper winding of relay 38, springs 1f!A and5 of'key 39, Afront Contact and armature 'l of relay 46, springs 6 and 8of key'BZ, springs l`2 and i3 of key 39, springs il and li cf vkey 6lback contact and armature @-f''relay 8, front Contact and armature 5 ofrelay 45, to the ring of plug l! it elleomrters battery in the :circuitof the attendants connector. Likewise, a clzcult'may be traced from.battery on 'the ring 'of cord 31 springs 5 and 4 of key 3],lowerwinding of relay 38, springs H and l0 or key 3S, front Contact andarmature 2 of relay 4U, 'springs 5 and 3 of key 62, springs 3 and 2 ofkey M, springs' 3 and 2 of Ekey El, back contact and armature 3.0i relay45 frontcontact and armature 4 of .relay l5 .to

the tip of plug 42 where it encounters ground in the-circuit` of theattendantsconnector. Relay 3S responds and closes Va circuit fromgro-und, resistance 6,8, armature and front contact of relay 33,armaturev land back contact of relay 59, lower winding of relay 41,springs 8 ,and 9 Vof key 39,

front contact and armature of relay 45 to cause the operation of relayt1.,

Relay 38 will release when the dial is moved off normal but relay 59will not operateand relay 41 will release since the talk and dial key 62is operated. ,Moving the dial ofi normal separates the front and rearcords. The attendant then dials the two digits to direct the vconnectorto the desired line.

The attendants connector cuts through on the called line if it is idle,removing the battery and ground from the tip and ring and changing thejack sleeve resistance associated with the front cord to a lower value.Thus relays 44 and 46 will operate but relay 4i. remains operated undercontrol oi relay 3Q. The tip and ring of the front cord are thenconnected to back contacts of tripping relay 51 for the transmission ofringing current. The calling lamp 5l will also light at this time.

When theV called station answers the tripping relay 51 operates andcloses through the tip and ring of the front cord. The ground that locksrelay 51 operated also passes over lead 69 to the telephone circuit andcauses a relay therein to operate and furnish talking battery to thecalled station until the talking key is restored by the attendant. Whenthe talk and dial key 62 is restored to normal the battery and groundfrom the central cnice is fed through the windings of relay 38 to thecalled station. Relay 38 will operate and extinguish the callingllinelamp 5i at this time and relaylil will operate, opening'the shortcircuit about resistance 1U whereby less current from the central oiliceline is drained by the bridge and a greater amount allowed to flow tothe called station. The operations in this connection may now besummarized as follows: (A)V Talking battery for the called station isiurnished from the central office. (B) A high resistance bridgeconsisting ofthe winding of retardation coil 68 in series withtheresistance 19 is bridgedv across the tip and ring of the rear cord. (C)The supervisory relay 33 is under control of the called station.

When the receiver is replaced on the switchhook at the called stationthe circuit functions, as described hereinbefo-re, except that relay 38is under control ci the called station and the operation of relay i9causes the front supervisory lamp to light as a disconnect signal andshortcircuits the resistance 10, thereby decreasing the resistance oftheV bridge'across the-cord.

VFlashing recall is controlled by relay 38 in conjunction with relays l1and 49, as described hercinbefore. However, sincerelay 35 is notoperated the supervisory lamp 5| of the calling cord is flashed ratherthan theanswering cord lamp 32. l

, If the called station is busy the sleeve becomes lewin resistance andthe battery and ground are removed from the tip and ring inthe connectorand replaced by a bridge which is intermittently applied. If the talkand dial key G2 has been restored to normal the application of thisbridge will cause the supervisory relay 38 to operate and release,thereby starting the flashing recall signal on the front cord lamp.Ifthe attendant has not restored the talk and dial key TELEPHONE ANDDIALING CIRCUIT ARRANGED USE WITH ATTENDANTSCONNECTGRS,

When the tip of an associated cord, for instance, plug 62, is touched tothe sleeve of a busy station line, tie trunk, attendants connector ortrunk jack, ground or positive potential from the busy sleevecharges'condenser 1l through a winding of the repeating co-il 12 andresistance 13 to the front contact of relay 14, this relay beingenergized through the transmitter 15 of the telephone set. This inducesa busy click through the winding of the repeating coil 12 at theattendants telephone receiver.

Fos

Talking When the talk and dial key 62 of an associated cord circuit isoperated the leads 15 to 80, inclusive oi the telephone and dial circuitare Connected to the cord circuit, thereby closing the tip, ring andreceiver leads and providing a talking circuit for the attendant. Theattendants tran.,- mitter circuit may be traced from ground, theright-hand winding oi repeating coil 8i, through the tip of jack 82,transmitter 15, the tip of jack 83, the winding of relay 14 to battery.Speech currents from the transmitter 15 are then transmitted by theleft-hand windings of repeating coil 8l, through the back contacts 'andarmatures 2 and 4 of relay 84 to the talking conductors 85 and 8E. Theoperators telephone receiver circuit may be traced from conductorthrough the back contact and armature of relay 81, back contact andarmature l of relay 84, the sleeve of jack 82, thetelephone receiver 88,the sleeve of jack 83, armature 3 'and back contact of relay y84, themid-point tap on the left-hand winding of repeating coil Si through thecondenser 89, back contact and armature 4 of relay 84 to conductor 35.Through the back contacts and armatures of relay 9i) this talkingcircuit is connected to conductors and 11, leading to the front cord 42.Through the armatures and contacts of relays 9i and t2 this talkingcircuit is connected to conductors 18 land 19 leading to the tip andring of the rear cord 3 l Dialing In order to dial on a cord circuit thetalk and dial key 62 of the cord circuit is operated'. When the dial ismoved ofi normal relay 93 operates in a circuit which may be traced fromground, springs 2 land 3 of key 94, the orf-normal springs of the dial95, winding of relay 83 to battery. Through its front contact andarmature 2 relay 93 shortcircuits resistance 93. The operation of relayS3 also results in the operatic-n of relays 91, 81 and 90. The circuitfor relay 91 may be traced from battery, winding of relay S1, frontcontact and armature 3 of relay 93 to ground. The circuit for relay 81may be traced from battery, winding and this relay thereupon'fullyoperates Aand attracts all of its armatures.

In its normal condition a from battery, tact of` relay |09, through theback contact and armature 3 of relay IIS to the idle indicating lamp II3. Therefore, upon the operation of relay |09 this idle indicating lampis extinguished and the battery connection is extended by armature 270irelay |00 to its front contact to cause the lighting of the next idleindicating larnp.

Upon the operation of relay |88 the tip conductor is extended overarmature I and front Contact of relay |08, the upper left-hand windingof repeating coil I2I, back contact and armature 4 of relay H0, theupper winding of relay I|2 to ground. In a similar manner the ring ofjack |01 is extended from armature 2 and front contact of relay |08, thelower left-hand winding of repeating coil |2I, back contact and armatureE of relay IIO, the lower winding of relay H2 ,to battery. Due to areversal in the cord circuit hereinbefore explained, relay IIZ becomesoperated. The operation of line relay H2 connects the windings of thepolarized relay IM to the distant connector circuit which has arelayfacing the line to this trunk circuit. vThis connection may be traced asfollows: from ground, through the lower `winding of relay IIB, armature2 and circuit is established.

front contact of relay IIZ, vthe lower right-hand winding of repeatingcoil IZI, conductor I i5, back contact and armature 4 of relay |23 toconductor |25 and a similar circuit from battery, the upper winding ofrelay IIII, armature I and front contact of relay H2, the upperright-hand winding of repeating coil |2I, conductor IE6, baci; contactand armature I of relay |23 to conductor IM. Relay H4 operates in vthiscircuit and rcauses the operation of relays II1 and IIS. A circuit maybe traced from battery, contact and armature 3 of relay IIE), armatureand left-hand contact of relay I I4, armature and back contact ofrelayIIS, armature 1 and back contact of relay I I0 to ground. Relay I I1, inoperating, connects ground through its armature 2 and front contact tothe winding of relay I i8.v

When the attendant dials, relay ||3 follows the dial pulses and opensthe line 'to the 4distant The polarized it releases.

dial pulses as repeated by connector each time relay IIA follows therelay ||2 but the slow-release relay operated.

When dialing is completed the distant connector circuit inserts a highresistance into the line causing relay IM to release. relay IM causesthe release of relay |II which, due to the slow releasing characteristicH8, results inthe operation of the cut-through relay IIB. from ground,armature I relay |09, armature 2 and and front contact of front contactof relay H8, back contact and armature I of relay II1`,

the winding of" relay ||0 to battery. Relay'I I0 locks through itsarmature 5 and iront contact and the iront contact and armature I ofrelay |09 to ground.

The operation of relay H0 causes the resistance in the sleeve lead tochange from high to low. Up to this time the winding of relay |09 whichhas a high resistance is connected to the sleeve of jack |01 but uponthe operation of relay IIS a lower resistance IZIJ` is placed inparallel with the winding of relay |00 so that the marginal relay 44 inthe cord circuit now becomes operated. The operation of relay III) alsothrough armature 2 and back conwinding of relay I I1, back Ill .n0-ldsThe release of of relay A circuit for this relay may be tracedv connectsa condenser |20 across the middle of the side of the repeating coilfacing the distant connector and prepares a circuit for connecting thewindings of relay H4 with polarity reversed to the leads of the distantconnector throughV normally closed contacts oi' relay H2 and thewindings or" the diiferential relay IIE?. The operation of relay I I0opens the circuit of relay |I2 so that this now releases. Relay IIO alsoprepares a circuit for giving a closure to the cord circuit through thecontact of the polarized relay IIs.

The change in the sleeve resistance to the cord circuit resulting in theoperation of the marginal relay s causes the cord circuit to send outringing to this trunk. The ringing current causes relay E22 to operatewhich results in the operation of relay |23, thus causing a clear pathfrom the tip and ring oi the jack |01 to the line conductors IM and |25,respectively.

when the called party answers or when the distant connector connects alow resistance ground to the ring lead as a line-busy indication duringthe ringing interval, the tripping relay in the oord circuit operatesand removes the ringcurrent, causing relays |22 and |23 to release. Therelease of relay |23 again places the polarized relay H4 incircuit toOperate over the station loop if the line is idle. If, on the otherhand, the line is busy and the operation just described has been causedby a low resistance ground to the ring lead, then the differential relayIIQ will be unbalanced as a busy indication and instead of connecting abridge across the tip and ring of jack |61, will now connect interruptedground to the ring of jack |01, leaving the tip thereof open. ln caseonly relay H4 operates a signal that the called party has answered,acircuit may be traced from the tip of jack |01, armature I and frontContact of relay |03, the upper left-hand winding of repeating coil I2I,front contact and armature 1 of relay ||0, back contact and armature ofrelay I9, left-hand contactv and armature of relay IIs, armature 3 and.1, front contact of relay III), the lower left-hand winding ofrepeating coil |2I, front contact and armature 2 of relay |08 to thering of jack |01. In case the signal coming from the distant connectoris a low resistance ground on the ring, thereby causing the relay ||0also to operate, a connection may be traced from the ring of jack itl',through armature 2 and front contact of relay E33, the lower left-handwinding of repeating coil |2I, front contact and armature 3 of relay II0, armature and left-hand contact of relay IMI, armature and frontcontact or relay H0 through retardation coil |21 and interrupter E23 toground. Upon the iirst open period of this circuit, the flashing recallcircuit in the cord will be prepared for operation and then put intooperation upon the next closure thro ugh the interrupter |28. Thereafterthe signal displayed in the cord circuit will be modied by theinterrupter |26. Since this is of one-half the rate of the interruptercausing the iiashing recall signal, the result will be a totallydifferent kind of visual signal in which the display is of approximatelythree-tenths of the period and the dark condition of the lamp isapproximately seventenths of the period. In other words, every otheriiash of the lamp in the iiashing recall circuit will be eliminated. Asmentioned hereinbefore, the interrupter |28 is synchronized with theinterrupter 66 of the cord circuit so that the relation between the twos xed.

aannam nished through the windings of relays. H4, HS

and the repeating coil I 2 l.V The contacts of relay H4 maintain a.closure toward the cord circuit and relay IMY Will receive switchhookflashing from the called par-ty to the cord circuit so, that a flashingrecall condition may be set up in the ordinary manner by the subscriberreached through the distant connector.

When the plug is removed from the jack, relay |99' releases causing therelease of relays |08 and m. The release of relay HG causes the releaseo f relay H1' and relay IH, except that this latter relay may havealready released ldue to the called partyhanging up. Therelease of relay||1 causes the release of relay H8 which causes the idleindicatingrlamps to lig-ht and restores the circuit from the lowerlwinding of relay |08 to the ring of the jack |01 so that it can operateon the next call,

Connector circuit for completing calls from attendant at distant privatebranch exchcmg to station Zines-Fic `(i Upon the seizure of the circuitshown in Fig. Sand the operation of the line relay- Hlthereat, batteryand ground are connected through the windings of relay H4 to theconductors |24 and |25 which extend to. the upper andV lower windings,respectively, of vline relay |29. Relay |29 operates from batter-y onthe tipr and ground on the ring of Vthe trunk circuit and causes theopleration of the rst slow relay |30 in preparation for pulsing'. v c

n the first open period relay |28 releases and establishes a circuitfrom its armature I and' back contact, through armature Iv and frontcontact of relay |39', springs i and 3 ci the vertical oil*- normalspring combination |3|,` through the windings of slow-release relay |32and the vertical magnet |33 to battery. Relayl |32 operatesY before thevertical magnet'steps the switch, opens the circuit of relay |34 andcloses its own locking circuit to spring of the vertical oi-ncrmalsprings |3|. When the switch steps and the vertical oir-normal springsoperate, the original operating circuit for relay |32 and magnet |33will bejopened but a substitute circuit throughrthe armature of relay|32 will be closed in its placev Without interrupting thesteppingcireuit. When the line relay |29 reeperates theuvertical magnetreleases, but relay |32 being slow to release holds until the end of thetrain of impulses comprising the rst digit.v

The switch thus continues to step Vertical until the end of the traination o1' relay |129 releases relay |32.

@n the second digit, ywhen relay |23 releases, relay |34 and the rotarymagnet- H operate. The circuit maybe tracedifrornarmature and backcontact of relay |29z armature and front con,- tact of relay |33.,springs 6 and 5 oi the. vertical oli-normal. spring combination |3|',armature and hack. contact of relay |33. armature .4 and hack contact Qfrelay |36, through the Winding c f relay |34 to batteryand in paralleltherewith through armature 4 and hack contact of .relay l 31 ,ano thewinding of rotary mascot |35 to battery.

The rotary magnet and relay |34 oro multiple and the lotterrcloy bci-.nsslow to reloose remains operated during pulsing while the rotary mas.-nct stops the switch. to the desired terminal.

of impulses when the oper"-V armature: of relay |34, front Contact oTesting the linee-.Eine busy Whoo the switch is on the line to which it.has been dialed'anol before theslow-rcleose. relay |34. releases. thcSleeve ofthe called lino is concocted to relay |38. A circuit maybetraced frein hattcry through the Winding of relay |38, front contact andarmature. Z of relay |34'. Slccyck brush |39. to the `sleeve terminal ofthe called 01.1 a busy line the sleeve will be grounded. therebyoperating relay |38., When' relay :3.4 releases, relay |38. locks.through tho normal. contacts. of and. armaf ture 2 or relay |38.armature 3 and front contact of. the lrst slow-reIeasing relay |34izo-ground.

Relay |8.'o1o.crote.d; opens the circuit of relay |31 and operates relay|36- '.Ihis circuit may bo trascorrono battery., Winding of relay |36',

ture .3 and baal; Contact of relay |.3!|,.fro1 1.t contact and armature3 of relay A|.3-l to ground. Relay |36 operated, (1l cocos the circuitof; relay |31| and the circuit oi rotary .magnet |35, (2,), removes theline relay f2.9. from thc tio and rms, thereby causing the release. olrelay |23. and (3.2 connects high resistance relay MQ through thearmature and'bacl; contact of relay |4. and the. front. Contact, andarmature of relay |36, to the tip wire |24, and high resistance relay|42. through armature. 5. and back Contact of rcloy |43, the.. front.VContact and armature 4 of relay |36y to. the rins'conductor |25. Relay|42 oporates to ground on the ring, at the distant. end of the trunk andholds the first slow relay |34@ operated.

Removing the lino; relay |29 from the tip and ring is 'a signal to thetrunk. at the distant private branch exchange. to prepare, to ring, orto receive busy ashes and Wherrtlie trunk is thus prepared it reversesbattery and ground to the connector circuit. Relay |42 thon releases andrelay |40 thon operates.. Relay |40 closes resistance |45 across thewindings of relay ,|23 which thereupon operates and holds the rst Slowrelay |30. opel',- ated.Y Relay |29. also completes the circuit to relay|43 through tho armature 2 and front contoot of relay |29, armature 3and, front oontactof relay |36, to ground. Upon operating. relay |43establishes a' Connection from ground, armature 2 and front contact o1'relay |43, front contact andarmature of relay la to the ring conductorAextending'to the Vcnitgoing trunk circuit, Fis.' 5. whore itrcsults inunbalancing the differential relay IS for the purposes hereinheforodescribed.

When thc called lie is idle, the sleeve brush |39 will encounter abatteryvconncction instead of ground andrelay |3l| in releasing at theend of the rotary stepping movement connects relay |31 to. thesleovehrush. This circuit may bo traced from sleeve brush |39 througharmature 2 and back Contact ci relay` |34, upper winding of relay |37,back contact and armature 2 of-relay |38, armature il and front Contactof the rst slow. relay vitil. Relay |31 becomes sufficiently energizedin this circuit to move its armature 2 which closes a circuit fromground, armature 2 and frontcontact of relay |30, front Contact andarmature 2 of relay |31, lower Winding of relay |371, through rotarymagnet t0 battery.V This causesv the frull energization of relay |31 andat the same time stops iurthor action of the rotary magnet. VRelay* |31connects direct ground .for- Ward to the line circuit sleeve throughits. ,front contact and ormaturc to hold. tho out-.oli relay of thecalled lino and to busy the terminal to other switches.- Relay |31 alsoopens the original energizing circuit -or the `rotary magnet and opensthe release path through its armature 1. Through its armatures and 3.relay |31 partially closes the tip and ring rconductors tothe calledstation; L v

Upon the release of relay |34 and thevoperation of relay is'i, a circuitis established from ground through the front contact and .armature 5. ofrelay ll, back Contact and armature 3 of relay |35 tothe winding ofrelay |36. As hereinbefo-re described, relay |36,'upon operating,Yremoves the line relay |25 from the tip and 1ing and closes the twohigh resistance relays |40 and |42, respectivelyjto the tip and ringofthetrunlc.v Relay |42'holds irst slow relay |39 operated until batteryis reversed by the trunk circuit atY thev private branch exchange. Relay|42 then releases and relay |45 operates. Relay |40 again causes theoperation of the line relay |29 to complete the circuit to relay |43which now" operates.V Relay |43 operated connects the tip and ringer thetrunk from the distant private branch exchange to the tip and ring ofthe called station. The tip conductor |24 may be traced through theVupper winding of the supervisoryrelay |42, through armature I and frontcontact of relay"|ll3, front-contact and armaturey i of relay |31 tothetip brush |45 of the connector which is now in association with the ltip of thev called line |51. The ring conductor '|25 may be tracedthrough the lower winding of relay'lflfl, armature and front contact ofrelay |43, front contact and armature 3 of relay E31 to the ring brush|42 of the connector leading tothe called subscribers lstation |41.Relay |43, in operating, opens the circuit of relay |42 but relay |40 isstill connected to the tip so that the linerelay |29 remains operated.

During the ringing of the station frornrthe distant private branchexchange, relay |50 holds to the ringing ground on the tip.. Relay |44,whose lower winding is in series withthe ring, may .operate on thealternating currentand operaterelay Edil. This will Vopen the windingofre'lay |50 .but its lower contacts perform the sarne function as thelower contacts of relay HilllsoV that theline relay |25 remainsvoperatedto'hold the connection. When the called fstationanswera. ringing istripped and relay |44 operatesv on the station loop to remove relay |45from the connection and hold the connection through the operation ofrelay |4| as described. vUpon disconnection by the called station relay|44 'releases and causes relay |4| to release, but relay |40 thenoperates to ground on the tip to hold the switch. When the cordrispulled down at the private brauch exchangev after the called stationdisconnects, relay |40 will release thus releasing the line relay |25and the first slow relay |30. Relay |35, in releasing, opens the circuitfor relay |31 and now acircuit may be `traced from ground, armature land backcontact of relay |20, armature and back contact of relay |30,back contact and armature 'l or relay |31, springs |l and 2 of thevertical oil-normal spring combination |5 to release magnet |49 andbattery. Release magnet |49 is operated and causes the brushes 145, |48Vand |39 to leave their position inconnection with the terminals of thecalled line. Thus, the'switch is returned to no rmal. The release ofrelay |31 causes the release of relay |36 and the release of relay |28causes the release of relayV |43,

0n disconnection 'by the attendant from a busy connection, relay Mainreleasing, releases the line relay |26 and the first slow relay |35.Relay |35 then releases relay |35 which, in turn, releases both relaysil and |43. Withrelay |30 released, the release magnet te restore theswitch to normal.

Connector circuit-Rotary hunting-For completing from attendant atdistant private branch archange to station Zines-Fi/- 7 rihe operationof this connector is in many respects similar to the operation oi theconnector in` Fig. 6. When the attendant at the distantV private branchexchange selects this trunk', the lineA relay |56 operates trom batteryon the tipy and ground on the ring of the trunk circuit at the distantprivate exchange. Relay E50, operated, operates thefirst slow relay |52which prepares the circuit for pulsing, f On the iirst open period relay|56 releases operating the second slow relay |52 in series ywith thevertical magnet |53, through the springsof the vertical ofi-normalcontact cornbination |54. Relay |55 being slow to release will remainoperated during pulsing; Relay |52 operates before the vertical magnetsteps the switch, opens the circuitof relay |55 and closes its ownlocking circuit to the vertical oiuior- .al springs. When the switchsteps and the vertical cit-normal springs operate, the originaloperating circuit of relay |52 will be opened but the holding path willbe completed without interrupting the stepping circuit. When the linerelay |55) reoperates, the vertical magnet releases but relay |52 beingslow to release holds until the end of the digit. The switch thuscontinues to step vertically until the end o 'he digit when theoperationof relay |55 releases relay |52. -On the second digit when the linerelay |50 releases, relay 55 and the rotary magnet operate. Relay |55being slow to release holds over pulsing while the rotary magnet stepsthe switch to the desired. line terminal which may loe-either anindividual line or vthe first yor" a `group of lines. Y

Before relay |55 releasesat the end of rotary stepping a path is closedfrom the sleeve Wiper |56 of the connector switchvthrough armature 2 andfront contact of relay |55, armature Vand back contact of relay |51 tothe winding of relay |53 and thence to battery.l A busy line will haveground on the sleeve which will operate relay |58. When relay |55releases, relay |53 locks to the sleeve ground through its armature 4and front contact and the normal contacts of armature 2 of relay |50 tothe sleeve wiper |56. Re-

lay |58 at this time causes the operation o1 relay |60 in a circuitfrombattery, winding of relay |60, back contact and armature of relay|55, front contact and armature 2 of relay |58 to conductor I6! suppliedwith ground over armature 2 and front contact of the first slow relay|5| Relay |60 operated, (l) opens the circuit of relay |55 and thecircuit of the rotary magnet |62;

(2) removes, the line relay |56 from the tip and ring which nowreleases; (3) connects high resistance relay |53 to the ring conductor|25 and high resistance relay |64 to the tip conductor |24; and (Ll)closes a circuit from relay |65 which may be traced from battery, thewinding of relay |55, armature and back contact of the rotary magnet|62, normal contacts of varmature 2 of relay |05, front contact andarmature 5 of relay |58, armature and front contact of relay |60,

